某同学旅游时,划船行在两山之间的湖面上。他大喊了一声,经过1.2 s听到一个回声

题型:计算题

问题:

某同学旅游时,划船行在两山之间的湖面上。他大喊了一声,经过1.2 s听到一个回声,又经过3 .6 s听到了另一个回声,问:两山相距多远?(设当时的气温为15℃。)

考点:声音的传播声音的产生
题型:计算题

DSA检查的禁忌证不包括()

A.严重的心、肝、肾功能不全

B.高热、急性感染及穿刺部位感染

C.肺炎治疗后

D.女性月经期及妊娠3个月以内者

E.严重的动脉血管硬化

题型:计算题

根据每句话的意思以及首字母填入恰当单词,使得句意连贯。

1. We usually have a d__________ when we don't agree with each other.   

2. She is now in hospital because of her serious d__________.   

3. The teachers usually d________ our class into several groups when we have activities.   

4. I always have a bad d__________ when I'm tired before sleeping.   

5. How far is the e__________ from the sun?   

6. August is the e__________ month of the year.   

7. When I'm in trouble, my parents always e__________ me.   

8. The film is so interesting! I really e__________ it!   

9. He is e__________ in English. He often gets the highest score.   

10. Everybody is here e_________ Tommy. He's always late.

题型:计算题

通常利用脂质体的哪种特点来改进易被胃酸破坏的药物

A.避免耐药性

B.降低药物毒性

C.提高药物稳定性

D.提高疗效

E.降低药物水解能力

题型:计算题

西北干旱农业区和青藏高原农业区的相似之处是 [ ]

A、都是畜牧业为主

B、都大量种植耐寒喜凉的农作物

C、都盛产亚热带水果

D、都发展绿洲农业

题型:计算题

如图,光滑竖直杆上套有质量为M=0.7kg的滑块,通过轻质细绳跨过光滑滑轮与质量为m=0.5kg的物块相连.滑轮上边缘到竖直杆的距离L=4m,开始时细绳右半部分保持水平.由静止释放滑块M,当M沿杆下滑h=3m时,滑块M下滑的速度是多少?(设细绳足够长,不计空气阻力.g=10m/s2.)

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